Off-road vehicles, such as JEEP® WRANGLER® vehicles, are continually being driven in more demanding terrain in addition to paved roads and highways. The wide range of driving conditions includes dirt and gravel roads, 4×4-only trails, off-road parks with large rock and log obstacles, desert roads, stream beds, water crossings, and manmade obstacle courses. These extreme terrain conditions require more effective suspension control, particularly designed with modified suspension systems that increase suspension travel and allow for larger tires.
A well-known configuration for a suspension system for off-road vehicles includes a coil spring in conjunction with a shock absorber at each wheel. Exemplary embodiments of such a configuration are shown in FIGS. 7 and 12, wherein FIG. 7 shows a front suspension system 16, and FIG. 12 shows a similar rear suspension system 18. Referring to FIG. 7, the illustrated front suspension system 16 will be described with the understanding that the illustrated rear suspension system 18 of FIG. 12 operates in a similar manner.
As shown in FIG. 7, a coil spring 20 is disposed between a spring cup 22 and a spring tower 24 in a generally vertical position. The spring cup 22 is fixedly secured to the vehicle chassis 26 and includes a downward facing opening to receive the upper end of the coil spring 20. The spring cup 22 limits both upward vertical movement and lateral movement of the upper end of the coil spring 20 relative to the chassis 26. The spring tower 24 is fixedly mounted relative to the axle housing 28 of the vehicle and includes a base 30 that engages a bottom surface of the coil spring, as well as a tower portion 32 that extends into the lower end of the coil spring. The base of the spring tower limits movement of the coil spring in a downward direction relative to the axle, while the tower portion limits lateral movement of the coil spring relative to the axle.
With the upper end of the coil spring fixed relative to the chassis and the lower end of the coil spring fixed relative to the axle, the coil spring 20 compresses and expands to absorb motion of the associated wheel caused by irregularities in the surfaces upon which the vehicle is traveling. At the same time, the shock absorber 34 acts as damper to dissipate the energy absorbed by the spring. Thus, the coil springs 20 and shock absorbers 34 cooperate to allow the vehicle chassis to ride relatively undisturbed while the wheels follow the road, thereby improving both the ride and the performance of the vehicle.
In off-road driving conditions, vehicles are often subjected to extreme bumps or dips in the trail. The resulting impact to the tires can compress the spring to the point where part of the chassis would impact the axle housing, potentially damaging one or both components. To mitigate the risk of such impact damage, bump stops 36 are often installed to act as bumpers that prevent the chassis from directly impacting the frame.
The factory bump stop designed for JEEP® WRANGLER® vehicles 1997-current (2016 expected) is a microcellular foam bump stop 36 that is secured in a bump stop cup 38 to extend at least partially beyond the opening of the top cup. The bump stop cup 38 containing the bump stop 36 is secured to the lower end of a bump stop support 40, which is mounted on the frame side so that the bump stop extends downward toward the axle when the bump stop cup 38 is secured to the bump stop support 40. As shown in FIG. 7, the front bump stops 36 extend down through the center portion of the coil springs 20 and contact a top portion of the spring tower 24 when the coil springs are compressed beyond a certain point. Referring to FIG. 12, the rear bump stops 36 are positioned beside the coil springs 20, and when the coil springs are compressed beyond a certain point, the one or more of the bump stops contacts the associated bump stop fittings 42 that are mounted to the axle housing.
When a bump stop is engaged, it contacts the axle housing and, in effect, dampens the impact between the metal chassis frame and the metal axle housings. However, the factory bump stop is merely an elastic bumper and does not provide adequate suspension control for extreme terrain.
Therefore, there exists a need for improved suspension components for JEEP® WRANGLER® vehicles, as well as for other vehicles, that provide effective suspension control for extreme conditions. There also exists a need for improved suspension systems that, in addition to suspension control for extreme conditions, also provide a high level of comfort and drivability on normal highway conditions.